#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
using namespace std;
const int N = 220;
char s1[N], s2[N], t1[N], t2[N], ans[N];
int main()
{
	while (scanf("%s%s",s1,s2)!=EOF) {
		memset(ans, 0, sizeof(ans));
		memset(t1, 0, sizeof(t1));
		memset(t2, 0, sizeof(t2));
		int len1 = strlen(s1);
		int len2 = strlen(s2);
		int k = 0;
		for (int i = len1 - 1; i >= 0; i--) {
			t1[k++] = s1[i] - 'A';
		}
		k = 0;
		for (int i = len2 - 1; i >= 0; i--) {
			t2[k++] = s2[i] - 'A';
		}
		int flag = 0;
		for (int i = 0; i < 220; i++) {
			ans[i] = t1[i] + t2[i] + flag;
			flag = ans[i] / 26;
			ans[i] %= 26;
		}
		int i = 219;	
		for (; i >= 0; i--) {
			if (ans[i]) {	
				break;
			}
		}
		for (; i >= 0; i--) {
			cout << (char)(ans[i] + 'A');
		}
		cout << endl;
	}
	return 0;
}